Dissection of the LS Engine

Discussion in 'Chevy' started by Toobuilder, Sep 28, 2012.

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  1. Mar 30, 2013 #41

    Jan, thanks for the reply on the prop question. Is there a source where I could find a formula for computing the thrust of different props and pitch combinations?


    Thanks to the guys for the other replys also. I have looked quite a bit at creating power with a direct drive LS engine. The turbo certainly has its benefits, but it does
    add some weight and lots of heat to deal with. Then tuning the engine to work with it becomes somewhat complicated. In the instance I'm looking at, I will be trying
    to build as simple a combination as possible and most likely use injection. I want to emulate an aero engine with low rpms. Weight will be a major concern in the airplane
    I want to build......so anything that adds even more weight is a non-consideration for me. The LS6 engines are hard to find and have been surpassed by the newer LS
    versions. The LS7 complete is way too expensive for most people ($13000). On the other hand, if someone purchased a readily available LS3 type block with a 4.000 inch
    stroker crank, they would have 415 cu in. Cubic inch increase is the easist way to increase power in these blocks with minimal change in weight. Cost for the assembled
    block/crank/pistons is about $4200. Since you don't need high flowing heads, used LS1 heads should provide all the air needed for an engine only turning 2700 rpms.
    I have talked to some knowledgeable automotive industry experts and they agreed with my concept and even gave me some suggestions for cam choices. Something also
    available is the Cam Calculator that Comp Cams has on line. You might play with that a little. To buy a new complete LS1 these days will probably run you about $5800.
    Going the stroker route would allow you to basically assemble an engine for $7000 that had far more power for the same weight. You can easily find used LS1 heads for $200
    (or less) an intake with injectors for anothe $200 or less. Buy a new cam and lifters and a Rattler or Fluid Damper.......and you have a much more usuable combo. Did I mention
    that the rotating assembly will also be more robust than the factory units? Now look at some of the new plug and play computers or SDS and you have a purpose built combo
    that will easily produce 235/260 hp @2700 rpms. Also, the compression ratio can be selected to run cheap gas wwith a 9.5 comp ratio vs the higher stock LS1 ratio.
    Now, the question becomes how to couple all the power I need for my particular airplane, to the propeller. This is why I feel a direct drive with a short shaft coupling will save
    weight and a reduction drive ($5-7K) (80 lbs) is not the best choice......for me anyway.
     
  2. Mar 30, 2013 #42

    RJW

    RJW

    RJW

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    Toolbuilder, your thread is in danger of becoming a battleground for this interminable argument. Don’t you guys remember the last forty times you talked about this?

    A 6-liter V8 makes (again) about 180HP around 2700RPM. Amazing how this is so close to the power that a 6-liter Lycoming or Continental makes. You can get about 200-220HP from this displacement at 3200RPM. If you try to get more power at this speed using boost, compression, or “torque” cams be ready to run racing fuel. And a prop that works at 3200RPM will give you takeoff performance in a conventional 2-place not a lot better than a Long EZ.

    I’ve mostly retired the idea of inexpensive DD unless it’s done with minimal expectations and the dangers of a low thrust prop in an airframe that will support the weight of a V8 are acceptable. Bolt a hub to the crank, use a very light prop in a slippery airframe, make sure you have a long runway, pucker your butt, and go flying. But if something like the performance that we are used to is desired then a gearbox or a stroker will be needed.

    A light gearbox, designed for transmitting affordable power—about 250HP, is the best compromise. It offers the best chance of getting these motors in the air with acceptable performance.

    Aside from the above, which I’m sure all of us already know, what’s going on with your dissection, Toolbuilder?

    Rob
     
  3. Mar 30, 2013 #43

    Toobuilder

    Toobuilder

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    If the goal is to emulate an aero engine, I think the LS needs to be built like an aero engine - big displacement, low RPM. Thats not to say a higher RPM, more "standard" engine driving a small diameter prop won't fly, but that's not my particular focus. Unfortunately, a super large displacement, but low RPM engine really does not exist anywhere in the motorsports world. The parts certainly do, but its going to take one of us to lay out the cash and build one. Until we do that, we're going to be stuck in theory. Nothing wrong with throwing ideas out there, however.

    As for my project, it has dropped down the priority scale for a bit, but is not forgotten. Not by a long shot.
     
  4. Mar 30, 2013 #44

    rv6ejguy

    rv6ejguy

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    You really can't do much with cams at 2700 rpm, the VE is already well over 90% here and you are going to need 120%+ to get this power without more cubes. Turbos are way cheaper than redrives- about $800 for the turbo, intercooler core $100-$250, 321 for exhaust probably $500, some other aluminum elbows etc. $100. But it is more weight and you start looking at the power to weight ratios again, cubes, the extra cost of those parts. DD is cheap but the power to weight ratios are never attractive. If someone comes up with that cheap, light, reliable redrive as RJW says and we can spin the engine to 4000, things look very rosy then. All those compromises...

    This discussion prompted me to study DD engines for my projects but after working the numbers, weight, power I come right back to the redrive. You just end up with a boat anchor engine and a bunch of lead in the tail to even get anywhere close in performance and that is even with a turbo. If you can spin to maybe 3200 to 3500 rpm with a special prop like Gary Spencer and Reg Clarke, things are good. I just have to get the redrives to work well. I have not had any failures in mine but there are some things I am not happy with. Have to see how the latest mods work.
     
  5. Mar 30, 2013 #45

    Toobuilder

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    Did you work the numbers with big inches, or standard displacement? After looking into the LS series, there really is a lot of options out there. It will quickly surpass the traditional SBC for aftermarket support IMHO.
     
  6. Mar 30, 2013 #46

    rv6ejguy

    rv6ejguy

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    I was looking at bigger displacement Subes in my case, the LS is simply too heavy even for the RV10 and the thrustline with a V engine is no good for an RV unless we invert it. I think with the right airframe and giving up some takeoff distance with a smaller prop It could be alright. I'll be interested to see what you come up with and how it works if you decide to got ahead with it, costs to.:)

    Gary Spencer's Long Ez is one of the few DD atmo conversions that works very well with really good overall performance compared to a Lycoming. So certainly an aluminum V8 can do well if all the details are taken care of.
     
  7. Mar 31, 2013 #47
    I pretty much agree with you. The thing about using a different cam than a large displacement engine usually comes with is that the OEM cams are usually compromises that have to work thru a larger rpm range. While changing the cam to a specific use in a smaller rpm range will not give someone the "100 hp increase" that cam manufacturers like to advertise, it can bring an additional 20/30 hp into that range which is very useful. GM makes big block engines to run continuously in the oil and gas industries that
    have been optimised for a specific range, so that demonstrates some benefit being available. If you look at the torq line for these engines its very flat....which is what I would try to emulate. Also, the roller cam used in these engines allows the valve to open faster and close later due to increased ramp profiles on the cam when compared to what a flat tappet aircraft engine can do. This would also allow more complete cylinder filling, hence more available power within the rpm range. Each detail of converting has to be analyzed for an additional small gain that builds toward an overall solution. Thats the plan that the Carbon Cub uses and its a huge success. I recently read something about how detailed they were in their creation of the CC, examing minor things that when added to the overall combination produced a liteweight airplane. There probably aren't any of the quick easy solutions that are going to make an auto engine viable, but each detail can help.
    I have conversed with Gary Spencer previously and he seems to have a setup that works well. Most of what we say is speculative until one of us shows, like Gary that it can/will work.

    The thing about weight is that with a water cooled V8, we all have to accept the fact that it is going to weigh more than all but the largest air cooled aero engines. We also need to decide how many horsepower can we actually use in the aircraft we want to hook it to. Those of you who have read any of Ben Haas's postings may remember that he had to shorten his propellor because his engine produced so much power that it actually tried to rotate the airplane. Apparently there was not enough resistance to the torque available that old axiom about an "equal but opposite reaction" reared its head. I wonder about this when people want to be able to throw excess horsepower in an effort to correct a mistake in operating their aircraft. There are probably some new engines which are lighter and could use a turbo. I know there is at least one alum Buick/Olds that flies well with one. I have a Rover (Buick/Olds) sitting in my shop thats been modified to accept Buick bearings that I could build a 300 cu in engine with....but for now I'm still looking at something that is more readily available (LS Chevy). There is a 100 lb difference and probably a 100 hp difference as
    well.

    I need to do some other stuff right now, So HAPPY EASTER everyone.
     
  8. Mar 31, 2013 #48

    Toobuilder

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    Concerning weight, the LS is certainly heavier than a 540 Lyc, but that maybe too broad a characterization. First off, the angle valve 540 is quite a heavy engine, and the 520/550 Conti is even worse. Second, the LS engine has a lot of integrated accessory drive equipment. GM made this stuff plenty stout to reduce vibration, and its all included in the basic weight of the engine. Lots of that automotive junk just falls right off with the removal of a few bolts. So I think that using a detail oriented approach to the "aero" version of the LS, the weight might just surprise us all. It may never be a featherweight, but it might get into the ballpark.
     
  9. Apr 1, 2013 #49

    captarmour

    captarmour

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    I was just about to ask about the rover V8. I rebuilt one for a range rover years ago and I remember lifting the empty block with one finger. And I alone could easily lift the short block. I never did find out the weight of one of these. They have been around for a long time and can be tuned for many different configs. They wear fast when oil changes are few and far between when they silt up and wear the cams. The one I rebuilt showed very little wear but the lifters and cam were shot. Maybe a bored and stroked with very short duration high lift cam might work well in an aircraft.
     
  10. Apr 2, 2013 #50
    You will find the Buick/Olds/Rover engine to weigh about 300 lbs complete. The later model Rover has several displacements with the largest being about 280 cu in. The blocks for some of the Rovers feature 4 main bolts with 2 of them entering from the side in a manner similar to an LS1 Chevy. The crank is raised into the block on all versions from Buick/Olds thru Rover versions. Remember this was originally developed by GM so the LS1 appears to have adopted that feature rather than invented it. The Rover crank appears to be rather robust but Rover apparently only makes standard size bearings........so if you need to turn the crank, you are out of luck. The main bearing saddles for the Rover are of a slightly different diameter from the Buick/Olds engines and will not accept undersize Buick/Olds main bearings. The block can be align bored (.020 ? appx) to accept the Buick/Olds bearings and allow turning the rover crank or acquiring a Buick 300 crank. Check out a site called D&D Fabrication which specializes in stroked and stock versions of these engines. It requires different rods and pistons and some (getting rare) aluminum Buick heads to make it work. This engine can fly well when inverted for thrust CL reasons. There are other discussions about this engine conversion and a nice example of a fellow who flies behind one and later added a turbo to his conversion. Steve Wittman proved it to be a venerable setup with direct drive.
     
  11. Apr 2, 2013 #51

    captarmour

    captarmour

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    Thanks for that detailed info. 300 lbs is heavier than I thought, I must be stronger than I thought. I'll do a couple searches.
     

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